The invention relates to photography and photographic equipment and more particularly relates to a multiple position lens barrel having commonly biased first and second lens carriers.
A great many zoom lens barrels and other multiple position lens barrels are available that provide accurate and precise positioning of lens groups using complex and costly mechanisms. Those lens barrels are unsuitable for inexpensive cameras, particularly one-time-use and other simple cameras. With simple cameras, mechanisms used typically have a small number of parts that are relatively easy to manufacture and simple to assemble.
One of the complexities of some zoom lens barrels arises from a requirement of moving two different lens groups (a xe2x80x9clens groupxe2x80x9d has one or more lens elements) relative to both the focal plane and each other, in accordance with particular optical designs. A solution is the use of different, but linked mechanisms to move the two lens groups. In U.S. Pat. No. 5,673,099, a cylindrical tube has a pair of differently shaped cam grooves. Cam followers joined to the two different lens groups follow respective grooves and move the lens groups accordingly, when the cylindrical tube is rotated relative to the lens groups. U.S. Pat. No. 6,369,956 is similar, but separates cam grooves onto different components. U.S. Pat. No. 5,216,549 discloses a lens barrel that uses a rib in place of a cam groove. U.S. Pat. No. 5,225,939 discloses a lens barrel that has a single component having a rib for one follower on an inside wall and a groove for another cam follower on an outside wall. This lens barrel has a reduced number of pieces in comparison to the others mentioned above, but has complexly shaped pieces.
U.S. Pat. Nos. 3,672,280 and 5,289,320 disclose lens barrels having spring urged lens positions. These mechanisms are relatively simple and, the case of U.S. Pat. No. 5,289,320, include use of a cam follower and cam. These lens barrels have the shortcoming of being limited to movement of a single lens group.
It would thus be desirable to provide an improved lens barrel and method in which a relatively small number of relatively simple parts can move two different lens groups relative to the focal plane and each other.
The invention is defined by the claims. The invention, in its broader aspects, provides a multiple position lens barrel that has a first lens carrier defining an optical axis. The first lens carrier has a set of first cam followers. A second lens carrier is aligned with the optical axis. The second lens carrier has a set of second cam followers. A cam cylinder has a tubular wall surrounding a passage aligned with the optical axis. The cam cylinder has a set of one or more first cam tracks and a set of one or more second cam tracks. The first and second cam tracks are axially spaced apart. Each cam track extends away from the wall in a radial direction. Each cam track extends along and about the optical axis. A biaser biases the cam followers toward respective cam tracks.
It is an advantageous effect of the invention that an improved lens barrel and method in which a relatively small number of relatively simple parts can move two different lens groups relative to the focal plane and each other.